Radio-frequency-sputtered AlN acts as a negative type electron- and ion-beam resist with high-resolution and high dry-etch durability. Fine structures of silicon (30-50 nm wide) with high-aspect ratio ( > 10) have been fabricated using the AlN resist with electron-beam lithography and succeeding low-temperature dry etching with SF6 at -130-degrees-C. They were thermally oxidized at 800-degrees-C to reduce the size further. Structures less than 20 nm have been obtained.